Good stuff. Plenty of very succesful and reliable model subs have been built on the old Darnell box, but I'm personally more a fan of cylinders.

If you have access to a lathe, then making the endcaps for a cylinder should be straightforward.

Material wise you can use PVC or acrylic pipe. The latter offers a see-through cylinder, but it is more expensive and fragile- if you drop in something hard it will most likely crack or at least chip, whereas PVC will bounce. In the States, Polycarbonate is very popular. Like acrylic it's transparent, but is much tougher, in fact, AFAIK it's the strongest thermoplastic. Unfortunately it's very expensive here in the UK, especially for the larger diameters which is why acrylic is more popular. It gets the job done, although not a good idea to use it with gas systems.

PVC pipe is readily available in various sizes. A large boat like the Type VII will easily accomodate 110mm diameter pipe, I often see lots of this chucked out in skips, but you can also purchase a length new for very little. Endcaps can be machined from sheet plastics like ABS, acrylic, polycarbonate or you can even machine them from materials like aluminium. I would avoid wood, as it's difficult to seal well and water always seems to find a route in somewhere or other.

Shaft seals can be turned on the lathe, or you can purchase ready made. They're not ultra expensive, so if you're unsure about making those vital components, it's worth looking at the commercial units which work very well.

Hi KazzerI had no idea this guy was living on my doorstep! Very useful to know, so thanks.As for the boat, no she was based in Bedfordshire. I picked her up one frosty morning from a bloke called Charles in Milton Keynes.As for the mods - I have looked at the cylinder set up as advised by sub, but I am looking at over £400. Out of range post-Christmas I'm afraid. So I am now looking to replace the rear ballast tanks by building some bigger ones out of acrylic to hold about 900ml. This with the existing snorkel arrangement will at least enable me to sail at Decks Awash while I get used to her - and hopefully achieve the odd dynamic dive. Then, maybe later in the year, I'll look into the cylinder ballast tanks. I am quite well off for r/c model shops round here with two excellent outlets - Lesro in Christchurch and Westbourne models in Bournemouth.I have found the help and advice in here really really useful so go into 2013 emboldened to get out onto the water as soon as she's out of dry dock!Poole Park here I come....Happy New Year to all.Mark

Poole Park brings back memories. I used to live just down the road at Sherwood Ave. I used to ride my bike to work right across Poole Park Boat pond, it was actually frozen over - salt water too. 1963 - 15' deep snow drifts across Dorset and so darned cold, the winter freeze went on for months.What about some photos of the innards of your new acquisition?

I take it you were looking at a readymade cylinder for £400, which is not what I suggested in my post. Material cost,assuming you have all the electronics, you can knock a zero off that price, and if you can find a piece of pipe chucked out, it could cost quite a bit less.

When you purchase a commercial unit, you are paying mainly for labour and expertise. Model submarines is still, by and large a cottage industry. It tends to be one or two man bands working away in garden workshops. The products are low quantity and employ labour rich methods of production. Consequently the price is high, especially when compared with other sectors of modelmaking, which have benefitted from mass-manufacturing.

Some modellers lack the workshop equipment to make such units. Others don't want the hassle of building something like this, they'd sooner purchase a proven unit and concentrate on working on the outer hull, which entails more traditional modelling skills.

Blimey Kaz - 1963. You do have a good memory! I lived in Northants then - in Kettering - and it was bloody cold there too! But at Wicksteeds they always used to drain the big and small boating lakes for the winter for some reason so no ice there. (Not sure if they still do.) I'll pass your greetings on to Poole boating pond when I get there. And yes - I'll try to post some pics of the U Boat's innards on here.

Sub - thanks for your comments. I hear what you are saying about it being an expensive hobby if you aren't handy yourself. And for very good reasons.I am going to read the files you sent me tonight more closely so hopefully will get some ideas from there.

Just watch that pond in Poole Park. Last time I was there it was full of 3 feet long carp feeding on Canadian Goose Poop. Those birds are the scourge of modern parklands. You can't step anywhere for them, and the water - well, more like soup. You might not like your boat once its been in there! The bigger pond is saltwater, so that will cause you more problems.

We have millions of those darned geese here in New York too. Breed like flies, and unfortunately they infest the canal where I live. We've been bombed a few times. I use a catapult to shoo them off my lawn - good sport!

Saltwater is terrible stuff. It tarnishes and rots anything metallic, meaning you need to engineer your boat from the best materials, and hose it off well after each run. You will also need an external aerial on the receiver that projects above the waterline to maintain a signal.

Hmm - good points both.I work closely with 180 odd SW schools so I will have to persuade one of my friendly headteachers to lend me their school pool for the odd weekend!I take it chlorine is not as bad as salt water?Poole to New York Kaz? Interesting move!M

Chlorine is not as bad. The radio signals can be received underwater. The higher the chlorine content the more interference, I found. There are many that survive sailing in winter months by using a pool.

If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

Chlorine is not the problem. It is the total dissolved solids in the water, due to poor water chemistry maintainence . This is from minerals, oil and other crud from human skin. Salt chlorination systems are a whole different problem.I use an electronic TDS meter when in a swimming pool. The signal will weaken when the TDS level is above 700 parts per million.

Well, thanks for all the advice chaps. It's been extremely valuable.I have decided that in the interests of post-Christmas austerity I am going to rebuild the exisiting ballast tanks out of acrylic (making the aft tanks lower, larger and more robust to match the forward tank) and stick to the original snorkel and tubing system for now.It's been great fun trying stuff out and thinking things through so thanks for the tips.I am going to end this thread now as it's getting a bit long.Thanks again. This is a great forum (and kaz - I will post some pics when I've worked out how to do so!)CheersMark

Mark V11c wrote:...........Thanks again. ........... kaz - I will post some pics when I've worked out how to do so!CheersMark

Looks like this site doesn't host photos, so you'll need to load them to something like POSTIMAGE.ORG then link to them here.

Cripes! That was easy! Just click on the link below the box you're typing into, where it says PostImage (automatic fill-in) and follow along. You can always use preview if you don't want to go public yet.